Chronic swelling of a limb is a medical condition that results in pain, tissue breakdown and immobility for many patients. Such swelling is often caused by venous insufficiency or other disease such as lymphedema. In the case of venous insufficiency or venous stasis, the venous system of the extremities, particularly the lower extremities, experiences reduced blood flow. The reduced blood flow results from venous dysfunction in the extremity that limits the effective return of blood from the extremity back to the heart. The problem is exacerbated in lower extremities due to the effect of gravity, which must be overcome to move the blood back to the heart. However the arms are also susceptible to chronic swelling conditions such as may be caused by cancer of the lymph glands or post-mastectomy radiation treatment.
A common treatment for chronic swelling is the application of external pressure to increase tissue pressure in the region. This treatment decreases the swelling and improves tissue oxygenation, thereby allowing tissue to heal. In applying pressure to the leg, it is desirable to apply the highest pressure at the ankle and gradually decrease the pressure that is applied toward the top of the lower leg. However applying pressure to the limb can be problematic for a patient that also suffers from poor arterial perfusion. Poor arterial perfusion is caused by insufficient blood supply and blood has difficulty reaching the limb, not just returning from the limb as with venous insufficiency. Applying pressure to the limb serves to help prevent blood from ever reaching the limb. Therefore, traditional methods of treating chronic swelling cannot be used for patients with poor arterial perfusion.
A known means for applying pressure to the limb to treat chronic swelling is highly elastic bandages or multiple wrappings (in the case of devices for the foot and leg). The wrapping is wrapped tightly around the limb to apply pressure for the purpose described above. The wrappings generally must be applied by a caregiver. After initial treatment, elastic stockings are used by the patient to continue preventative treatment. The stockings do not need to be wrapped about the limb, however, they must be stretched over the limb, including the foot, ankle and calf in order to be donned. A disadvantage of these devices is that they are difficult for a user, particularly an elderly or disabled user, to stretch onto the limb for suitable therapeutic benefit. Also, the wrappings and elastic stockings constantly apply pressure to the limb when they are worn without a mechanism for selectively discontinuing the pressure they apply. Thus patients that also suffer from poor arterial perfusion cannot use the wrappings and stockings because there is no way for them to periodically discontinue the pressure to allow blood to flow to the limb.
Another approach to treatment of chronic swelling has been to apply pressure to the limb with a fluid. An advantage of using a fluid to apply pressure is that it readily conforms to the unique contours of a limb and can be applied easily by a user. U.S. Pat. No. 4,805,601 (Eischen) and U.S. Pat. No. 5,711,760 (Ibrahim et al.) disclose lower limb coverings having air bladders for applying pneumatic pressure to the limb. Other pressure applying devices use the pressure applied by a liquid surrounding the limb. U.S. Pat. No. 3,977,396 (Cartier) discloses an apparatus using liquid pressure, which comprises a tub filled with liquid mercury into which the patient places the limb surrounded by an impervious flexible wrapping to prevent contact with the mercury. The pressure applied by the liquid mercury around the surfaces of the submerged limb is believed to provide treatment for the chronic swelling condition of the limb.
Another treatment device described in U.S. Pat. No. 5,759,164 (Pacey) uses hydrostatic pressure applied to the limb by a liquid tight bag wrapped around the limb and filled with liquid. The flexible bag is filled with liquid to apply pressure to the limb by a separate liquid reservoir that is attached to the body above the limb and joined to the bag by a conduit